Heparins and low-molecular-weight heparins (LMWHs) have been the mainstay for the prevention and management of venous and arterial thromboembolic disease. In particular, the LMWHs have become well established in the past 15 years for the prevention of thrombosis in medium- and high-risk surgical and medical patients and in the initial management of venous thromboembolism (VTE). They have also been widely evaluated and adopted in clinical practice in the management of patients with acute coronary syndromes. More recently, a variety of heparin-like drugs have been evaluated as potential antithrombotic agents, and the synthetic pentasaccharide (fondaparinux) has been developed and evaluated for the prevention and treatment of VTE.